The consequences of slash-and-burn techniques for ecosystems are enormously destructive.The principal vulnerability is the nutrient-poor soil, pervasive in most tropical forests. When biomass is extracted even for one harvest of wood or charcoal, the residual soil value is heavily diminished for further growth of any type of vegetation.The area is an example of desertification, and no further growth of any type may arise for generations.
The ecological ramifications of the above scenario are further magnified, because tropical forests are habitats for extremely biologically diverse ecosystems, typically containing large numbers of endemic and endangered species. Therefore, the role of slash-and-burn is significant in the current Holocene extinction.
Some scientists believe that even the mighty Mayan empire succumbed to the effects of slash-and-burn farming. For years, the Mayans relied on this technique to survive in the tropical region now known as Guatemala. Scientists have determined that just before the Mayan empire fell -- around A.D. 900 -- widespread deforestation had resulted in a complete absence of tree pollen. The lack of trees in the area led to a temperature increase of roughly 6 degrees, which eventually brought about widespread drought. The drought signaled the end for the Mayans
Wilmar, named the “worst company in the world” by Newsweek, and 22 other oil palm companies are considered to be responsible for tropical deforestation.